Combustion chambers

ABSTRACT

The invention pertains to combustion apparatus for a gas turbine engine comprising a combustion chamber lying within a casing defining therewith a passage for the supply of air to the combustion chamber, an igniter situated in a recess formed in the wall of the casing, and a baffle situated in the passage adjacent and upstream of the igniter so that air flowing through the passage to the combustion chamber is induced by the baffle to form a stabilized vortex around the igniter.

United States Patent Champion [54] COMBUSTION CHAMBERS [72] Inventor: Keith Harold Champion, Rickmansworth, England I [73] Assignee: Rolls-Royce Limited, Derby, En-

gland 22 Filed: Dec. 16, 1970 21 Appl. No.: 98,837

[52] US. Cl. .Q ..60/39.82 P, 60/39.65 [51] Int. Cl. ..F02c 7/26 [58] Field of Search.....60/39.82 P, 39.82 S, 39.82 R,

[56] References Cited UNlTED STATES PATENTS 2,715,816 8/1955 Thorn et a1 ..60/39.65 2,592,110 4/1952 Berggren et a1. ..60/39.82 P 2,621,477 12/1952 Powter et al. ..60/39.82 P 3,540,216 11/1970 Quillevere et al. ....60/39.82 P

1451 Sept. 19, 1972 3,124,933 3/1964 Stram et al. ..60/39.82 P

FOREIGN PATENTS OR APPLlCATlONS 1,476,843 6/1969 Germany ..60/39.82 P 644,719 10/ 1950 Great Britain ..60/39.23 201,132 l/l955 Austria ..60/39.82 R

Primary Examiner-Carlton R. Croyle Assistant Examiner-Warren Olsen Attorney-Stevens, Davis, Miller & Mosher 5 7] ABSTRACT The invention pertains to combustion apparatus for a gas turbine engine comprising a combustion chamber lying within a casing defining therewith a passage for the supply of airto the combustion chamber, an igniter situated in a recess formed in the wall of the easing, and a baffle situated in the passage adjacent and upstream of the igniter so that air flowing through the passage to the combustion chamber is induced by the baffle to form a stabilized vortex around the igniter.

' 2 Claims, 3 Drawing Figures COMBUSTION CHAMBERS This invention relates to combustion apparatus gas turbine engines.

It is known in gas turbine engines to provide a compressor, combustion apparatus and turbine in flow series, the combustion apparatus comprising an air casing connected to receive air from the compressor and a combustion chamber situated within the air casing and apertured to receive air therefrom. The combustion chamber exhausts through the turbine.

It is known to provide a torch igniter in the space between the air casing and combustion chamber so as to form a pilot flame which is carried by the air flow into the chamber there to ignite fuel supplied by a main fuel supply.

In relatively small engines where the passage formed between the casing and the combustion chamber is a narrow one, for example less than 0.5 inch, there are difficulties in establishing stable combustion conditions for the torch igniter. It is an object of the invention to provide a combustion apparatus in which these combustion conditions in a relatively narrow space can be successfully maintained. It is also an object of the invention to provide an improved distribution of the pilot flame in said passage with a view to aiding the main combustion process.

According to this invention there is provided a gas turbine engine combustion apparatus comprising a first wall structure defining a combustion chamber, a second wall structure defining an air casing surrounding the combustion chamber, a passage defined between said wall structures and through which air flows in a determined direction, a baffle arranged in the passage transversely to said direction for inducing vortices at the downstream side of the baffle, and a torch igniter connected to the casing in a position downstream of the baffle for presenting fuel and ignition to said vortices for generating a pilot flame.

The combustion chamber may be formed to define a head so related to the igniter that at least a part of the air flow past the igniter passes from one side of the head to the other on its way to one or more apertures in the chamber.

Preferably the casing wall structure is formed to define a recess open to the passage and located directly downstream of the baffle, the igniter being situated within said recess.

An embodiment of the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is part sectional side elevation of a gas turbine engine.

FIG. 2 is a sectional view of the reverse flow combustion chamber shown in FIG. 1, drawn to an enlarged scale.

FIG. 3 is a part view in the direction of arrow C in FIG. 2.

Referring to the drawings, there is shown a gas turbine engine 11 comprising a centrifugal compressor 12, combustion apparatus 13 and a turbine 14 all in flow series as shown.

The combustion apparatus 13 comprises an annular combustion chamber 15 mounted within an annular casing 16 and supported from an anchor point 17 on the mainframe 18 of the engine.

A main fuel injector 19 comprise a Hike pipe' 20 connected to the wall of the combustion chamber 15 and projecting thereinto. The injector 19 includes a fuel supply pipe 21 connected to a fuel supply system 34 and passing through a hole 22 in the casing 16 and then through a hole 23 in the combustion chamber and terminating within the pipe 20. A flexible metallic seal 24 prevents air leaks between thepipe 21 and the hole 22.

Air supplied by the compressor 12 flows, as indicated by arrows 25, along a passage 26, defined between the combustion chamber 15 and the casing 16, into the combustion chamber through ports 30 and then exits through an outlet 27 of the combustion chamber to the turbine 14.

A torch igniter 28, comprising an igniter plug 31 and fuel injector 29 connected to an ignition supply 35 and an auxiliary fuel injector 31 connected to the fuel supply system 34, is situated in a recess 32 in the casing 16. A baffle 33 is attached to-a wall of the recess at a point upstream from the torch igniter and projects into the passage 26,

In operation the air flowing from the compressor through the passage 25 is induced by the baffle to form stable vortices 36 around the torch igniter to create a suitable environment for ignition to be effected and the resulting flame at the auxiliary fuel injector to be maintained. This pilot flame is continuously fed by the supply 34 and travels with the air along the passage 26 and into the combustion chamber 15, through ports 30 therein, where it ignites the mixture of air and the fuel from the main fuel injector 19.

The location of the igniter 28 is in a relatively narrow part of the passage 26 and upstream of the main fuel injector 19.

The narrowness of the passage, in this example about 0.3 inch, requires that the baffle 33 is substantially in the form of a flat plate inducing a pair of generally twodimensional vortices 36, and said narrowness therefore also requires the presence of the recess 32 to provide for an area of slow air movement necessary, together with the vortices, to maintain burning.

Since the igniter 28 is situated upstream of the injector 19 the pilot flame passes over the main fuel supply pipe 21 so as to raise the fuel temperature and improve vaporization in the pipe 20.

The igniter 28 is of course only actuated for starting of the engine, and is switched off once the main combustion is established.

Further, it will be seen that the pilot flame is distributed by the flow 25 around the head of the chamber, i.e. the area surrounding the injector 19 with generally beneficial results as regards raising the temperature of that area during starting.

The combustion apparatus is of the reverse flow type, that is, the mean direction of flow 36 within the chamber 15 is opposite to the general direction of flow 37 through the engine. The position of the igniter 28 must be upstream of the primary combustion zone, i.e. the zone in the chamber 15 surrounding the main fuel injector 19 and constituting the head, denoted 39, of the chamber. This means that the igniter must be situated in the relatively narrow passage 26 and the baffle and recess make this possible as already mentioned. At the same time this location of the igniter in a reverse flow chamber makes it possible for the pilot flame not only to travel over the main fuel injector 19 but also through the bend of the passage 26 around the primary zone and to the opposite side of the combustion chamber before entering the latter. In other words, the arrangement provides access by the pilot flame to either side of the head of the combustion chamber.

We claim:

1. Combustion apparatus for a gas turbine engine comprising a first wall structure defining a combustion chamber, a second wall structure defining an air casing surrounding the combustion chamber, a passage defined between said wall structures and through which air flows in a predetermined direction, a recess formed in said second wall structure and opens towards said passage, a baffle arranged in-said passage at the upstream end of said recess and transversely to said direction of air flow for inducing vortices at the downstream side of said baffle, and a torch ignitersituated within said recess for presenting fuel and ignition to said vortices for generating a pilot flame.

2. Apparatus according to claim 1 wherein said combustion chamber has a head defining a primary c0mbustion zone and extending therefrom so that the mean direction of flow in the combustion chamber is opposite to said predetermined direction, the passage extending around said head so that the pilot flame can pass from one side of the head adjacent the igniter to the opposite side of the head. 

1. Combustion apparatus for a gas turbine engine comprising a first wall structure defining a combustion chamber, a second wall strucTure defining an air casing surrounding the combustion chamber, a passage defined between said wall structures and through which air flows in a predetermined direction, a recess formed in said second wall structure and opens towards said passage, a baffle arranged in said passage at the upstream end of said recess and transversely to said direction of air flow for inducing vortices at the downstream side of said baffle, and a torch igniter situated within said recess for presenting fuel and ignition to said vortices for generating a pilot flame.
 2. Apparatus according to claim 1 wherein said combustion chamber has a head defining a primary combustion zone and extending therefrom so that the mean direction of flow in the combustion chamber is opposite to said predetermined direction, the passage extending around said head so that the pilot flame can pass from one side of the head adjacent the igniter to the opposite side of the head. 